The long-term objective is to understand neural control of hormone secretion and its impact on reproductive physiology and behavior using the marine mollusk Aplysia californica as an animal model. Because of their simple nervous system and large neurons, Aplysia have been widely used for biophysical, cellular and molecular investigations of the neuroendocrine cells (called bag cells) that control ovulation and egg-laying behavior. However, there has been little work on the processes that regulate hormone secretion from these cells. The proposed work will use bag cells and their secretion of egg-laying hormone (ELH) to identify cellular mechanisms that regulate dynamic changes in hormone secretion. The specific aims are to determine: whether patterns of bag-cell electrical afterdischarge and ELH secretion are similar between in vivo and in vitro preparations; and to determine the role of the diacylglycerol (DAG), calcium and cAMP in regulating ELH secretion.